Frost Dates for Flagstaff, AZ
In Flagstaff, AZ, the average last spring frost is around Jun 4 and the average first fall frost around Sep 28, for a growing season of about 115 days. For frost-tender plants, wait until Jun 19, when the chance of frost drops to 10%.
Based on NOAA 1991–2020 records from the Flagstaff Pulliam Airport, AZ weather station, 4 miles away, elevation 7,003 ft. Frost can come earlier in low spots and valleys and later near cities and large lakes.
Frost probability by date
Chance of a 32°F frost after the spring date, or before the fall date.
| Chance | Last spring frost | First fall frost |
|---|---|---|
| 10% | Jun 19 | Sep 16 |
| 20% | Jun 14 | Sep 20 |
| 30% | Jun 10 | Sep 23 |
| 40% | Jun 6 | Sep 26 |
| 50% | Jun 4 | Sep 28 |
| 60% | Jun 1 | Oct 1 |
| 70% | May 30 | Oct 2 |
| 80% | May 26 | Oct 5 |
| 90% | May 21 | Oct 9 |
Light frost vs. hard freeze
Average (50%) dates for each temperature. Tender plants are damaged at 36°F; most hardy crops survive until 28°F.
| Temperature | Last in spring | First in fall |
|---|---|---|
| Light frost (36°F) | Jun 16 | Sep 19 |
| Frost / freeze (32°F) | Jun 4 | Sep 28 |
| Hard freeze (28°F) | May 20 | Oct 9 |
Planting calendar for Flagstaff
Transplant Jun 11 – Jun 25
Transplant Jun 18 – Jul 2
Transplant Jun 18 – Jul 2
Transplant Jun 11 – Jun 25
Sow or transplant Jun 11 – Jun 25
Sow or transplant Jun 11 – Jun 25
Sow or transplant Jun 18 – Jul 2
Sow or transplant May 7 – May 21
Fall sowing Aug 3 – Aug 31
Fall sowing Aug 3 – Aug 24
Fall sowing Jul 20 – Aug 3
Sow or transplant May 7 – May 21
Fall sowing Jul 20 – Aug 17
Transplant May 21 – Jun 4
Fall sowing Jul 6 – Jul 20
Transplant May 14 – May 28
Fall sowing Jul 6 – Jul 20
Fall sowing Jul 6 – Jul 20
Fall sowing Aug 17 – Sep 7
Fall sowing Jul 20 – Aug 3
Plant May 7 – May 21
Based on the average last frost (Jun 4) and first frost (Sep 28). The dashed lines mark those dates. Seed packets list days to maturity; adjust for your varieties.